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How to check for an undefined or null variable in JavaScript?
...xistingObj.someUndefProperty. An undefined property doesn't yield an error and simply returns undefined, which, when converted to a boolean, evaluates to false. So, if you don't care about
0 and false, using if(obj.undefProp) is ok. There's a common idiom based on this fact:
value = obj.prop || de...
What's the best visual merge tool for Git? [closed]
What's the best tool for viewing and editing a merge in Git? I'd like to get a 3-way merge view, with "mine", "theirs" and "ancestor" in separate panels, and a fourth "output" panel.
...
Constructors vs Factory Methods [closed]
...ns: Elements of Reusable Object-Oriented Software by Gamma, Helm, Johnson, and Vlissides.
Use the Factory Method pattern when
a class can't anticipate the class of objects it must create
a class wants its subclasses to specify the objects it creates
classes delegate responsibility to one of sever...
How to use sed to replace only the first occurrence in a file?
...r if you prefer' solution. It would also be good to explain the answers - and to make the answer address the question directly, and then generalize, rather than generalize only. But good answer.
– Jonathan Leffler
Sep 29 '08 at 13:15
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Replace console output in Python
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An easy solution is just writing "\r" before the string and not adding a newline; if the string never gets shorter this is sufficient...
sys.stdout.write("\rDoing thing %i" % i)
sys.stdout.flush()
Slightly more sophisticated is a progress bar... this is something I am using:
d...
How do you performance test JavaScript code?
...e user/client. For example, we had a project with an Ext accordion that expanded to show some data and then a few nested Ext grids. Everything was actually rendering pretty fast, no single operation took a long time, there was just a lot of information being rendered all at once, so it felt slow to...
NUnit vs. Visual Studio 2008's test projects for unit testing [closed]
I am going to be starting up a new project at work and want to get into unit testing. We will be using Visual Studio 2008, C#, and the ASP.NET MVC stuff. I am looking at using either NUnit or the built-in test projects that Visual Studio 2008 has, but I am open to researching other suggestions. ...
Python circular importing?
... specific to your case: Try changing entities/post.py to do import physics and then refer to physics.PostBody rather than just PostBody directly. Similarly, change physics.py to do import entities.post and then use entities.post.Post rather than just Post.
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How do you cast a List of supertypes to a List of subtypes?
...er to another. However, you can cast through an intermediate wildcard type and it will be allowed (since you can cast to and from wildcard types, just with an unchecked warning):
List<TestB> variable = (List<TestB>)(List<?>) collectionOfListA;
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What does the “at” (@) symbol do in Python?
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An @ symbol at the beginning of a line is used for class, function and method decorators.
Read more here:
PEP 318: Decorators
Python Decorators
The most common Python decorators you'll run into are:
@property
@classmethod
@staticmethod
If you see an @ in the middle of a line, that's ...